I came up with this puzzle 16 years ago, it was on Ed Pegg's Mathpuzzle site but nobody solved it AFAIK. The 35 hexominoes (which look like this): are to be arranged, in groups of five, into seven shapes congruent to this one.

The sample above is not a useful shortcut, if you start like this you won't be able to do all seven. In theory you could do this without a computer. In practice... I couldn't.